Printing machines consume toner or ink when printing characters and images. A printing machine prints a gray area by scattering the small dots each having a width corresponding to multiple pixels on a white background. Reduction in consumption of toner or ink leads to a reduction in the number of times toner or ink is replaced. Toner contains polyester resin that is manufactured from oil. Reduction in the consumption of toner leads to a reduction in oil consumption.
There are conventional methods of reducing the amount of toner or ink that is consumed by printing machines. For example, there are reduction methods for uniformly reducing the amount of toner or ink that is consumed by a printing machine. In addition, for example, there are adjustment methods for adjusting the intensity of pixels, excluding the pixels in an edge, out of the pixels that are contained in image data.    Patent Document: Japanese Laid-open Patent Publication No. 2002-86805
However, the above-described methods have drawbacks in that image quality is decreased and the consumption of toner or ink cannot actually be reduced. For example, in the above-described reduction method, uniform reduction in the consumption of toner or ink leads to blurring of characters or images, which reduces the image quality. For example, in the above-described adjustment methods, most of the small dots in a gray area correspond to an edge and accordingly there are no pixels that can be adjusted in the gray area; therefore, the consumption of toner or ink cannot actually be reduced.